The present invention relates to a device for feeding fuel to a diesel engine, the device including a fuel storage tank, a pump provided in the conduit between the fuel storage tank and the engine and an injection pump for the atomizer(s), which latter pump is provided with a pressure control valve for reducing the excessive pressure to the pressure prevailing in the conduits and a device for measuring the consumption of fuel.
It is often important that the fuel consumption of vehicles and vessels be measured in an accurate way. The reasons therefore are the following:
1. Vehicles and vessels exist which include an auxiliary means, in addition to the engine, for propulsion, such auxiliary means being driven by the same engine.
Sometimes it is desirable to know the fuel consumption of each of the engines, e.g. because restitution of excise on fuel can be reclaimed or because one wishes to obtain an exact knowledge of the actual operation expenses.
2. Checks must be made to determine whether the fuel consumption of the engine is normal or whether there are any deficiencies which cause an excessive fuel consumption.
3. Mutual comparison of vehicles must be made for economic considerations.
4. Supervision of quantities of fuel purchased and of quantities of fuel used must be possible.
5. It is desirable to achieve optimal improvement of the type of driving with respect to economic use.
The measurements of the items 1-3 could be carried out by means of a temporary device including a guage on the vehicle. However, measurements according to items 4 and 5 require a more permanent construction of the measuring instrument.
It is usual to measure fuel consumption by one single flow meter.
If, however, only a flow meter is mounted into a fuel conduit system, two disadvantages are created:
A. Loss of power, which, possibly, could be compensated by increased fuel consumption.
B. Inaccuracy of measuring.
These disadvantages arise as follows:
A. A diesel engine always has a return conduit, by means of which the fuel being fed to the fuel pump and not being injected by the atomizers is returned to the fuel storage tank. If a gauge is placed in the fuel conduit system, care must be taken that no fuel is returned to the tank by means of the return conduit. The return conduit then must be linked up with the feeding conduit behind or downstream of the gauge. However, the temperature of the fuel returned is considerably higher than the temperature of the fuel in the storage tank. Such returned fuel would normally be cooled in the storage tank. When heated fuel is injected into the engine, the power thereof decreases since the injection is volumetrically constant, however due to the increased temperature the density of the fuel is less. Moreover, there are gas bubbles in returned fuel having an increased temperature, by which the effect of the loss of power of the engine is enhanced.
b. The feed pump creates a strongly varying flow rate (pulsing flow) in the fuel conduit system, involving over and under pressure conditions in the conduits. Also, the fuel pump must provide power for the operation of the gauge. An under pressure condition causes the formation of gas bubbles and therefore an inaccuracy of measurement, caused by the irregularity of the rate of feed of the injection pump.